ABSTRACT: The success of a P01 grant is highly dependent on the integration of the projects through a strong series of Shared Resource Cores. The Administrative Core (Core A) is proposed for renewal for the expressed purpose of providing leadership, administrative support and a framework of interaction for the planning, coordination, implementation and ongoing review of the individual research projects, cores and program of clinical trials to be conducted under the proposed P01. Core A will foster the scientific and clinical objectives of the individual projects and the P01 as a whole by conducting periodic meetings with the participating Project and Core Leaders to develop strategic plans and consensual decisions regarding program development and organizes periodic reviews of research progress and productivity by the Internal Executive Committee and the External Advisory Board. The core also maintains and facilitates communication between investigators in the individual projects and cores through regular conferences and research-in-progress presentations. Lastly, this Core provides fiscal management services for the projects and cores of the P01 and oversees all communication related to the P01 with the NCI. The Specific Aims for Core A are: provide organization and leadership for the P01 (Aim 1); provide general administrative and financial management for the individual research projects and cores (Aim 2); facilitate intra-programmatic interactions and communications through research conferences and periodic scientific reviews (Aim 3) and coordinate and provide oversight of scientific and clinical activities of the program (Aim 4). The Administrative Core will provide the necessary organizational support and leadership to aid the Project and Core Leaders in the accomplishment of the overall goal of the P01: to study both in mouse and man the mechanisms underlying the major complications of allo-HCT, including infections, GVHD and relapse, and develop novel therapeutic strategies to be tested in clinical trials in allo-HCT patients.